The present invention relates to a technique for analyzing inspection data in the manufacturing process of products, such as semiconductor devices, thin film magnetic heads and optical devices, in which particles can cause electrical defects.
A conventional technique will be described, by way of example, for performing an inspection in the manufacturing process of a semiconductor device.
Generally, a semiconductor chip production process is divided into a front-end process in which a plurality of chips, each having a circuit pattern in a unit chip, are multi-layered on a silicon wafer (substrate); and a back-end process in which the chips are diced chip by chip and individual chips are molded into complete products.
Most failures during the production process occur in the front-end process during which time work is performed to create fine features on the chips. It is important to improve the yield in the front-end process in order to reduce production costs. The yield referred to herein signifies the rate of non-defective products determined by the result of an electrical test representing the final test in the front-end process. In other words, it corresponds to the ratio of the number of non-defective chips to the number of all chips on the wafer.
In the front-end process, disconnection or short-circuit takes place in a circuit pattern because of particles generated during the production which degrade the yield.
Accordingly, reduction of particles is important for improving the yield.
To classify roughly, two kinds of inspections are conducted for the purpose of monitoring particles in the front-end production line. A first inspection called an in-line inspection, and a second inspection called an equipment quality control (QC).
In the in-line inspection, a wafer in production for an actual product is inspected on the production line.
Recently, for inspection of a wafer of a product during manufacturing, inconveniences actually caused in the product are monitored and its in-line inspection data is compiled with electrical test data to calculate an impact that particles have on a test object (a final product in the front-end process).
In connection with this procedure, one may refer to, for example, “Non-Defective Area Analysis for Quantifying Yield Impact” by is Ono et al, 1999, IEEE International Symposium on Semiconductor Manufacturing, Proceedings, pp. 127-130.
On the other hand, in the QC of equipments for production, the inspection is performed with attention to keeping the production equipment in good condition. A production equipment or unit is inspected before a wafer is brought into the production equipment and after the wafer is removed from the production equipment to measure a change in inspection results during the production process. Thus, particles and defects occurring in production equipments can be detected periodically for each equipment.